Description: The objective of the renewal project is to develop a comprehensive procedure to assess the human health risk associated with a Superfund site. Biological testing will provide data to define the immunotoxic, genotoxic, developmental and neurotoxic potential of environmental samples. Five experiments will be conducted as part of this project to evaluate the utility of a biologically-based protocol to estimate human health risk at a Superfund site. The first two experiments will assess the risk associated with complex mixtures from Superfund sites as well as model compounds and reconstituted mixtures representative of the AH and HAH chemicals. Experiment 1 is designed to compare estimates of human health risk using either biological or chemical analysis. This experiment will involve the collection of samples from Superfund sites and matched control areas. Environmental samples will be collected from a broad range of Superfund sites representative of AH (i.e. refinery waste, coal gasification waste) and HAH (i.e. wood-preserving waste, PCB contaminated soils and sediments) contaminants. An initial screen of site samples will be performed using an acute toxicity and two microbial genotoxicity assays. Selected samples will also be subjected to a quantitative GC/MS analysis. Based on the results of the preliminary screen, a limited number of samples will be analyzed in the battery of toxicological tests developed in Projects 1 through 6. A second experiment will be conducted to fractionate and isolate the most toxic components from selected complex mixtures. Isolated components will be reconstituted for testing (as individual compounds and mixtures) in the bioassays to evaluate the potential interactions of the components of a complex mixture. The data from these experiments will be used to provide biological test data describing the interactions of the components of complex mixtures and their potential toxic equivalency factors (TEFs). The third and fourth experiments will focus on monitoring detoxification of complex mixtures. These experiments will provide information to define the ability of remedial techniques to reduce toxicity and the potential threat to human health of complex mixtures in the environment. In the fifth experiment, phyllosilicate clays (natural and chemically-modified) will be evaluated for their abilities to tightly bind and detoxify target chemicals. The sites and molecular mechanisms of chemisorption will be elucidated.